JP2000261676A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device that can be applied to a tandem type and has a color/black and white automatic changeover function with superior productivity and image quality. SOLUTION: This color image forming device is provided with a color/black and white discriminating section 5 that discriminates whether a formed image is a color image or a black/white image on the basis of received image data, image processing sections 20, 21 that generate image data in YMCK for forming the color image and image data in K for generating the black/white image from the received image data, a page memory 11 consisting of 1st and 2nd page memories 110, 111 storing the image data in 5 colors, an output selection section 13 that selects the image data in YMCK stored in the 1st page memory 110, when the formed imaged is the black/white image or the image data in K stored in the 2nd page memory 111, when the formed image is the color image and an image forming section 3 that forms an image on the basis of the image data selected by the output selection section 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color image forming apparatus, and more particularly, to a color image forming apparatus having a function of determining whether an image to be formed is a color image or a monochrome image.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus such as a digital color copier, the content of image processing is switched between a color image and a monochrome image as a document to be formed. In recent years, it is automatically determined whether a formed image is a color image or a black and white image, and the content of image processing is automatically switched according to the determination result.
A color image forming apparatus having an automatic color / monochrome switching function is provided.

In this type of color image forming apparatus, an original image (formed image) is read prior to a normal image forming operation to determine whether the original image is a color image or a black-and-white image. There is known a method that employs a method for determining whether to operate in a processing mode suitable for a color image or a processing mode suitable for a black-and-white image based on a determination result (hereinafter, referred to as a “pre-scan method”). I have.

[0004]

However, in a color image forming apparatus employing the above-described pre-scan method, a scanning operation for automatic color / monochrome determination is performed before starting a normal image forming operation. However, there is a problem that the time until the image is output (hereinafter abbreviated as “FCOT”) increases and the productivity decreases.

As a countermeasure against this, for example, Japanese Patent Application Laid-Open No. 7-133
Japanese Patent Application Laid-Open No. 99-99399 discloses that in a color image forming apparatus that forms a color image by repeating an image forming process a plurality of times, the first color is set to black, and an image to be formed is formed during the first color (black) image forming process. Is a color image or a black-and-white image, and based on the result of the determination, it is determined whether or not to perform the image forming process for the second and subsequent colors. A "pre-scanless system" is disclosed.

However, in the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-13399, K (black), Y (yellow),
A device that forms a color image by repeating the same image forming process for each color of M (magenta) and C (cyan), for example, while forming an image of each color in order with a single photoreceptor unit, this is performed one by one. Although it can be applied to a device that forms a color image by over-transfer onto a transfer body, it is possible to use a color image corresponding to each color.
There is a drawback that the method cannot be applied to a tandem-type color image forming apparatus having one photoconductor unit. The reason is that, in the case of a tandem type color image forming apparatus, in order to increase the processing speed when forming a color image, K, Y,
Since the M and C images are processed in parallel (simultaneously) by the four photoconductor units, the color / monochrome automatic determination cannot be performed using the image forming process time of the first color (black). is there. Therefore, in a tandem type color image forming apparatus, a pre-scan method, which is inferior in productivity, has to be adopted.

In general, black suitable for forming a color image and black suitable for forming a monochrome image have higher density in black for black and white. However, Japanese Patent Application Laid-Open No.
In the case of the technique disclosed in Japanese Patent No. 3399, at the time when the first color image forming process is started (when the first color image is formed on the photoconductor), whether the image to be formed is a color image or a monochrome image is determined. Since the determination has not been made, it is necessary to determine in advance whether to process the first color black image for color or black and white. Therefore, if the first color black is processed for color, if the formed image is a black-and-white image, the density will be insufficient, and if the first color black is processed for black-and-white, When the image to be formed is a color image, the density of the black portion is too high, and the image quality is reduced.

In order to deal with such a problem, for example,
Japanese Unexamined Patent Publication No. 65530/1995 discloses a technique in which black processing of the first color is started for black and white, and if it is determined that the formed image is a color image during the processing, the processing is switched to color at that time. It has been disclosed. However, with this technique, although the lack of density in forming a black-and-white image can be resolved, when the black processing of the first color is actually switched from black-and-white processing to color processing, the black processing is not performed at the edge of the switching. Naturalness occurs, which leads to deterioration of image quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to be excellent in productivity, applicable to a dandem type, and capable of both color images and black-and-white images. It is an object of the present invention to provide a color image forming apparatus having a color / monochrome automatic switching function capable of forming an image with high quality.

[0010]

According to a first aspect of the present invention, there is provided a color image forming apparatus, comprising: input means for inputting image data based on an image to be formed; Determining means for determining whether the image to be formed is a color image or a monochrome image; and performing predetermined image processing on the image data input by the input means to form image data of each color for forming a color image. And a first storage unit for storing, of the image data generated by the data generation unit, the image data of each color for forming a color image. A second storage unit for storing the black image data for forming the black-and-white image; and the determination unit determines that the image to be formed is a color image. If it is determined that that the first
If the image data of each color for forming a color image stored in the storage unit is selected and the determination unit determines that the image to be formed is a monochrome image, the image data is stored in the second storage unit. Further, a configuration is provided which includes a selecting means for selecting the black image data for forming the monochrome image, and an image forming means for forming an image based on the image data selected by the selecting means.

In the color image forming apparatus having the above configuration, when image data based on the image to be formed is input by the input means, the color / monochrome determination based on the image data is performed by the determination means, The image data is subjected to image processing by the data generating means, thereby generating image data of each color for forming a color image and black image data for forming a monochrome image. The image data of each color for forming a color image is stored in the first storage unit, and the black image data for forming a black and white image is stored in the second storage unit. If the image to be formed is a color image as a result of the color / monochrome determination by the determination means, the image data of each color for forming a color image stored in the first storage unit is selected by the selection means, and When the formed image is a black and white image, black image data for forming a black and white image stored in the second storage unit is selected by the selection unit. Thus, regardless of whether the image to be formed is a color image or a black and white image, a black portion is generated at a density suitable for the image formation by the image forming means.

In a color image forming apparatus according to a second aspect of the present invention, an input means for inputting image data based on an image to be formed, and the image to be formed is colorized based on the image data input by the input means. Determining means for determining whether the image is an image or a monochrome image; and data generating means for performing predetermined image processing on the image data input by the input means to generate image data of each color for forming a color image A storage unit for storing the image data of each color for forming the color image generated by the data generation unit; and the storage unit when the determination unit determines that the image to be formed is a color image. The image data of each color for forming the color image stored in the image data is selected, and the determination unit determines that the image to be formed is a monochrome image. In the case where the image data of each color for forming a color image stored in the storage unit is combined, and the combined output is selected as black image data, An image forming means for forming an image based on the image forming means is employed.

In the color image forming apparatus having the above-described configuration, when image data based on an image to be formed is input by the input unit, color / monochrome determination based on the image data is performed by the determination unit, while The image data is subjected to image processing by the data generating means, whereby image data of each color for forming a color image is generated, and the generated image data of each color is stored in the storage unit. If the image to be formed is a color image as a result of the color / monochrome determination by the determination means, the image data of each color for forming a color image stored in the storage means is selected by the selection means, and the image to be formed is selected. If the image is a black-and-white image, the image data of each color for forming a color image stored in the storage unit is combined, and the combined output is selected as black image data by the selection unit. Thus, regardless of whether the image to be formed is a color image or a black and white image, a black portion is generated at a density suitable for the image formation by the image forming means.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a functional block diagram showing a configuration example of a color image forming apparatus to which the present invention is applied. The illustrated color image forming apparatus mainly includes an image input unit 1, an image processing unit 2, and an image forming unit 3.

The image input unit 1 is for inputting image data based on an image to be formed. For example, the image input unit 1 optically reads an image (formation image) of a document set on a document table, and corresponds to the read image. Receiving image data of a formed image transmitted from a scanner device for inputting image data or an external device via a network, a telephone line, or the like,
It is constituted by a communication function section for inputting the received image data.

The image processing unit 2 performs various image processing on the image data input by the image input unit 1. The image processing unit 2 includes an input tone correction unit 4, a color / monochrome determination unit 5, an enlargement / reduction unit 6, A spatial filter unit 7, a color space conversion unit 8, an output gradation correction unit 9, an error diffusion unit 10, a page memory 11, and a screen generation unit 12 are provided.

The input tone correction section 4 performs tone correction (gray balance correction, etc.) on the R (red), G (green), and B (blue) image data input from the image input section 1. . The color / monochrome determination unit 5 determines whether the formed image is a color image or a monochrome image based on the RGB image data corrected by the input tone correction unit 4. The enlargement / reduction unit 6 enlarges the RGB image data corrected by the input gradation correction unit 4 according to an image formation magnification (copy magnification or the like) set via a user interface (operation panel or the like) not shown. / Reduce.

The spatial filter section 7 reproduces an image that is faithful to the image to be formed.
The image data B is subjected to resolution correction processing (edge enhancement, smoothing, moire removal, etc.). The color space conversion unit 8 converts the RGB image data processed by the space filter unit 7 into Y (yellow), M (magenta), and M (magenta) by a color space conversion process based on, for example, an L ^* a ^* b ^* color system. The data is converted into C (cyan) and K (black) image data.

The output gradation correction section 9 corrects the YMCK image data converted by the color space conversion section 8 into gradation characteristics suitable for image formation. The error diffusion unit 10 performs pseudo halftone processing on the YMCK image data corrected by the output gradation correction unit 9 as necessary.

The page memory 11 stores the YMCK image data that has passed through the error diffusion unit 10 for each color in page units. The screen generation unit 12 generates a dot pattern based on the image data read from the page memory 11. The screen generation unit 12 performs a screen process when the read image data is multi-valued, and performs a smoothing process when the read image data is binary. After that, the image data is output in a range of, for example, 0 to 255.

The image forming section 3 forms an image based on the image data processed by the image processing section 2. FIG. 2 shows a configuration example of a tandem type. In FIG. 2, four photoconductor units 3 corresponding to each color of YMCK are shown.
0, 31, 32, and 33 are arranged side by side along the transfer belt. Each photoconductor unit 30, 31, 32,
At 33, the latent images formed by laser scanning from the optical unit 35 are each developed into a toner image by a developing device. Here, in the image forming operation in the color mode, each of the photoconductor units 30, 31, 32, and 33 performs YMCK.
Are formed, and these YMCK toner images are
After being sequentially superposed and transferred (multi-stage transfer) on the sheet on the transfer belt 34, the sheet is fixed on the sheet by the fixing unit 36. On the other hand, in the image forming operation in the black-and-white mode, a K toner image is formed only in the photoconductor unit 33, and after the K toner image is transferred to the sheet on the transfer belt 34,
The sheet is fixed on the sheet by the fixing unit 36.

FIG. 3 is a functional block diagram of the color image forming apparatus according to the first embodiment of the present invention. In the color image forming apparatus according to the first embodiment, the preceding image processing unit 20 includes the enlargement / reduction unit 6, the spatial filter unit 7, and the color space conversion unit 8 in FIG.
Are the output gradation correction unit 9 and the error diffusion unit 10 in FIG.
Is included.

The image processing unit 20 in the preceding stage converts the RGB image data input by the image input unit 1 and gradation-corrected by the input gradation correction unit 4 into color YM
The image data is converted into CK image data and black and white K image data. On the other hand, the image processing unit 21 at the subsequent stage
Of the image data of each color (for five colors) converted by the image processing unit 20 in the preceding stage, the image data of YMCK for color is subjected to image processing suitable for color image formation (for example, processing emphasizing gradation) And the like, and image processing suitable for monochrome image formation (for example, processing emphasizing character reproducibility) is performed on the black and white K image data, so that the YMCK image data for color image formation and the black and white image data are processed. K for forming
(Black) image data.

The page memory 11 is a first memory for storing, for each color, YMCK image data for forming a color image, out of the image data for the five colors generated by the image processing units 20 and 21 of the preceding and succeeding stages. A page memory 110 and a second page memory 111 for storing K image data for forming a black and white image are provided.

The output selection section 13 is provided with a color / monochrome determination section 5
By operating according to the determination signal given from
The page memory 11 (first and second page memories 110,
11) selectively outputs the image data for five colors stored in the multiplexer (MPX) 130 in the example shown in FIG.
And a change-over switch (SW) 131.

The multiplexer 130 performs a select operation in accordance with the determination signal from the color / monochrome determination section 5 to execute the color image forming K image data and the monochrome image forming K image data stored in the page memory 11. Is selected and output. The changeover switch 131 controls the output of the YMC image data for color image formation stored in the page memory 11 by a switching operation according to the determination signal from the color / monochrome determination section 5.

Next, an image forming process according to the first embodiment of the present invention will be described with reference to a flowchart of FIG. First, in step S11, the image input unit 1 inputs RGB image data based on an image to be formed (a document image or the like). The input RGB image data is subjected to gradation correction by the input gradation correction unit 4, and then the color / color data is input.
It is provided to the black-and-white determination section 5 and the preceding image processing section 20.

Next, in step S12, the above R
The color / monochrome determination unit 5 determines whether the formed image is a color image or a monochrome image based on the GB image data, and outputs the determination result as a determination signal. On the other hand, the preceding image processing unit 20 converts the RGB image data into
The image data is converted into YMCK image data for color and K image data for black and white, and supplied to the image processing unit 21 at the subsequent stage.
Then, the image processing unit 21 at the subsequent stage processes the image data supplied from the image processing unit 20 at the preceding stage in five colors at the same time, and generates the YMC for color image formation generated thereby.
The K image data and the K image data for forming a monochrome image are written in the page memory 11. At this time, the YMCK image data for color image formation is stored in the first page memory 110.
And the image data of K for forming a black and white image is stored in the second
Is written to the page memory 111.

If it is determined in the color / monochrome determination section 5 that the image to be formed is a color image (Yes in step S13), the changeover switch 131 corresponding to the determination signal is turned on. The switching operation (ON operation) and the selecting operation of the multiplexer 130 select the YMCK image data for color image formation stored in the first page memory 130, and the selected YMCK image data is stored in the image forming unit 3. (Step S14).

On the other hand, if the color / monochrome determination section 5 determines that the image to be formed is a monochrome image (No in step S13), a changeover switch corresponding to the determination signal is provided. Only the K image data for monochrome image formation stored in the second page memory 131 is selected by the switching operation (off operation) of 131 and the select operation of the multiplexer 130, and the selected K image data is converted to an image. It is output to the forming unit 3 (step S15).

Thereafter, the operation mode of the image forming section 3 (color mode / color mode /
(Black and white mode) is set, and an image forming operation based on YMCK image data for color image formation or K image data for monochrome image formation output from the output selection unit 13 is performed. (Step S16). Thus, when the image to be formed is a color image, a color image corresponding to the YMCK image data for forming a color image is formed on a sheet, and when the image to be formed is a monochrome image, A black-and-white image corresponding to K image data for forming a black-and-white image is formed on a sheet.

As described above, in the color image forming apparatus according to the first embodiment, the input RGB image data is subjected to image processing by the preceding and subsequent image processing units 20 and 21, and the color image formation generated by the processing is performed. While writing the YMCK image data for black and white and the K image data for black and white image formation into the first and second page memories 110 and 111, respectively, the image to be formed is a color image based on the RGB image data. Color / black and white determination unit 5
Therefore, even in a tandem type color image forming apparatus, the color / monochrome determination can be completed without pre-scanning and before the image forming section 3 starts image formation.

If the image to be formed is a color image as a result of the judgment by the color / monochrome judgment section 5, YMCK image data for color image formation is selected and output, and the image to be formed is converted to a black and white image. If the image is an image, the image data of K for forming a black and white image is selected and output. Black portions can be generated. Further, regardless of whether a color image or a black-and-white image is formed, the black processing (output density) is not switched from black-and-white to color during the operation of the image forming unit 3, so that the image quality is deteriorated accordingly. Can be avoided.

FIG. 5 is a functional block diagram of a color image forming apparatus according to a second embodiment of the present invention. In the color image forming apparatus according to the second embodiment, the preceding image processing unit 22 includes the scaling unit 6, the spatial filter unit 7, and the color space conversion unit 8 in FIG.
Are the output gradation correction unit 9 and the error diffusion unit 10 in FIG.
Is included.

The image processing unit 22 in the preceding stage receives the R which has been input by the image input unit 1 and has undergone gradation correction by the input gradation correction unit 4.
The GB image data is finally converted to color YMCK image data. On the other hand, the subsequent image processing unit 23 performs image processing suitable for forming a color image on the color YMCK image data converted by the preceding image processing unit 22 (for example, processing that emphasizes gradation). To generate YMCK image data for forming a color image, and the image data generated from the image data is stored in the page memory 11. That is, in the second embodiment, image processing is performed on the assumption that a color image is always formed regardless of whether the image to be formed is a color image or a black and white image. The YMCK image data is stored in the page memory 11.

The output selection section 14 is provided with a color / monochrome determination section 5
By operating according to the determination signal given from
The image data for four colors stored in the page memory 11 is selectively output. In the illustrated example, the combining unit 140, the multiplexer (MPX) 141, and the changeover switch (S
W) 142.

The synthesizing section 140 synthesizes the image data of the four colors YMCK stored in the page memory 11 by a process described later, and gives the synthesized output to the multiplexer 141 as K (black) image data. Whether or not to perform the data synthesizing process is set in accordance with a determination signal from the color / monochrome determination unit 5. Multiplexer 141
Is selected from the K image data for forming a color image stored in the page memory 11 and the K image data given from the synthesizing unit 140 by a selection operation according to the determination signal from the color / monochrome determination unit 5. One is selected and output. The changeover switch 142 controls output of YMC image data for color image formation stored in the page memory 11 by a switching operation according to the determination signal from the color / monochrome determination unit 5.

Next, an image forming process according to a second embodiment of the present invention will be described with reference to the flowchart of FIG. First, in step S21, the image input unit 1 uses RGB based on an image to be formed (eg, a document image).
Is input. The input RGB image data is subjected to gradation correction by the input gradation correction unit 4 and then supplied to the color / monochrome determination unit 5 and the preceding image processing unit 22.

Next, in step S22, the above R
The color / monochrome determination unit 5 determines whether the formed image is a color image or a monochrome image based on the GB image data, and outputs the determination result as a determination signal. On the other hand, the preceding image processing unit 22 converts the RGB image data into
The image data is converted into color YMCK image data and supplied to the image processing unit 23 at the subsequent stage. Then, the image processing unit 23 in the subsequent stage performs image processing on the image data supplied from the image processing unit 22 in the preceding stage in four colors simultaneously, and writes the YMCK image data for color image formation generated by this in the page memory 11. .

Next, when it is determined in the color / monochrome determination section 5 that the image to be formed is a color image (Yes in step S23), the multiplexer 141 selects according to the determination signal. Operation and Switching Operation of Switch 142 (ON Operation)
Thereby, the YMCK image data for color image formation stored in the page memory 11 is selected, and the selected YMCK image data is output to the image forming unit 3 (step S24).

On the other hand, when the color / monochrome determination section 5 determines that the image to be formed is a monochrome image (No in step S23), the synthesizing section according to the determination signal. 140, the select operation of the multiplexer 141 and the switch 142
Of the synthesizing unit 140 by the switching operation (off operation) of
Only the K image data generated by the synthesizing process is output to the image forming unit 3 (step S25).

Here, the synthesizing process of the image data in the synthesizing section 140 generates K image data (K image data with high density) suitable for monochrome image formation from YMCK image data for color image formation. The following four types of processing are conceivable.

In the first method, when the values of the four colors of the pixels read from the page memory 11 are multi-valued (0 to 255), the maximum value is selected and generated as K image data. It is a method. The second method is a method in which when the values of the four colors of the pixels read from the page memory 11 are multi-valued, the sum of them is calculated, and this is generated as K image data. However, when the sum of the values of the four colors is 255 or more, the value of the image data of K is set to 255 in each case. As a specific example, suppose that the image data of Y is “12”, the image data of M is “18”, the image data of C is “10”, and the image data of K is “180”. The image data of K having a value of “180” is generated from the synthesizing unit 140, and the image data of K having a value of “220” is generated in the second method.

In the third method, when the values of the four colors of the pixels read from the page memory 11 are binary, the values are converted into values corresponding to the reflectance of each color, and then the maximum value is selected. , Which are generated as K image data.
In the fourth method, when the values of the four colors of the pixels read from the page memory 11 are binary, the values are converted into values corresponding to the reflectances of the respective colors, and then the sum is calculated. This is a method of generating as image data. However, also in this case, when the sum of the conversion values of the four colors is 255 or more, the value of the K image data is set to “255” in each case. As a specific example, when the value of the image data of each color of YMCK is “0”, the conversion value is “0”, the conversion value when the image data of Y is “1” is “78”, and the image data of M is Is "138", the conversion value when the image data of C is "1" is "140", and the conversion value when the image data of K is "1" is "200". If so, in the third method, K image data having a value of “200” is generated from the synthesizing unit 140, and in the fourth method, K image data having a value of “255” is generated. Will be.

Thereafter, the operation mode of the image forming unit 3 (color mode / color mode /
(Monochrome mode) is set, and an image forming operation based on YMCK image data for color image output from the output selection unit 14 or K image data generated by the combining process is performed. (Step S26).
Thereby, when the image to be formed is a color image,
If a color image corresponding to the YMCK image data for forming a color image is formed on a sheet and the formed image is a black and white image, the K generated by the synthesizing process is used.
A monochrome image corresponding to the image data is formed on the paper.

As described above, in the color image forming apparatus according to the second embodiment, image processing suitable for color image formation is performed on the input RGB image data by the image processing units 22 and 23 of the preceding and succeeding stages. While writing the color image forming YMCK image data to the page memory 11, it is determined whether the image to be formed is a color image or a monochrome image based on the RGB image data. Since the determination is performed by the determination unit 5, even in the case of a tandem type color image forming apparatus, the
In addition, the color / monochrome determination can be completed before the image forming section 3 starts image formation.

If the image to be formed is a color image as a result of the judgment by the color / monochrome judgment section 5, YMCK image data for color image formation is selected and output, and the image to be formed is converted to black and white. In the case of an image, YMCK image data for forming a color image is synthesized so that the output density becomes appropriate, and the synthesized output is selected and output as K image data. Can generate a black portion at a density suitable for each of the color image and the black-and-white image. Further, regardless of whether a color image or a monochrome image is formed, black processing (output density) is performed during the operation of the image forming unit 3.
Is not switched from black and white to color, it is possible to avoid image quality degradation accompanying this. In addition to this, in the apparatus configuration of the first embodiment, it is necessary to add an image processing circuit that handles image data for black and white K, but in the apparatus configuration of the second embodiment, such an additional circuit is required. It can respond without a circuit.

In the first and second embodiments, when the image to be formed is a monochrome image, the switching operation of the change-over switches 131 and 142 (OFF operation).
Prevents the image data of the YMC for forming a color image from being output to the image forming unit 3. However, for example, the YMC of the YMC for forming a color image may be output regardless of whether the image to be formed is a color image or a monochrome image. The image data is transferred to the image forming unit 3
And if the image to be formed is a black and white image, the image forming unit 3 may employ a configuration in which the YMC image data is canceled, or the changeover switches 131 and 142
It is also possible to adopt a configuration in which the page memory 11 has the above function.

In the first and second embodiments, the tandem type color image forming apparatus has been described as an example.
The present invention is not limited to this, and is similarly applicable to an apparatus that forms a color image by repeating an image forming process a plurality of times.

[0050]

According to the color image forming apparatus of the first aspect of the present invention, it is determined whether the image to be formed is a color image or a monochrome image based on the image data input by the input means. By performing image processing on the input image data, image data of each color for forming a color image and black image data for forming a black and white image are generated, and these image data are stored in the first and second storage units. When the image to be formed is a black and white image, the image data of each color stored in the first storage unit is selected to form an image. When the image to be formed is a color image, 2 is configured to select black image data stored in the storage unit and perform image formation. Therefore, regardless of whether the image formation format is a tandem type or not, generation of a black portion without prescan is performed. Optimize density and color Any of the image / monochrome image can be formed with high quality. As a result, a color image forming apparatus having an automatic color / monochrome switching function, which achieves both excellent productivity and image quality, is realized.

According to the color image forming apparatus of the second aspect of the present invention, it is determined whether the image to be formed is a color image or a black and white image based on the image data input by the input means. Image data of each color for forming a color image is generated by performing image processing on the input image data and stored in the storage unit. If the image to be formed is a monochrome image, the image of each color stored in the storage unit is stored. An image is formed by selecting data, and when the image to be formed is a color image, the image data of each color stored in the storage means is synthesized, and the synthesized output is selected as black image data to perform image formation. With this configuration, regardless of whether the image forming format is a tandem type or not, the generation density of the black portion is optimized without pre-scanning, and both color images and black-and-white images are formed with high quality. It becomes possible. As a result, a color image forming apparatus having an automatic color / monochrome switching function, which achieves both excellent productivity and image quality, is realized.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration example of a color image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic diagram illustrating a configuration example of a tandem type.

FIG. 3 is a functional block diagram of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a procedure of an image forming process according to the first embodiment of the present invention.

FIG. 5 is a functional block diagram of a color image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a procedure of an image forming process according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image input part, 2 ... Image processing part, 3 ... Image formation part, 5
... Color / monochrome determination section, 11 ... Page memory, 13,1
4: output selection unit, 20, 22: preceding image processing unit, 2
1,23 ... the latter image processing unit, 110 ... first page memory, 111 ... second page memory, 130, 141 ...
Multiplexers, 131, 142 ... changeover switches,
140 ... Synthesis unit

Continued on front page F-term (reference) 2C087 AA15 BB10 BC02 BD07 BD35 CB13 DA02 2H027 EB04 FA28 FA30 2H030 AD07 AD08 AD12 5C077 LL16 LL19 MP01 MP08 NP01 PP27 PP28 PP32 PP33 PP38 PQ08 PQ22 5C079 HA11 HB01 NA03MA

Claims (2)

[Claims] 1. An input unit for inputting image data based on an image to be formed, and determining whether the image to be formed is a color image or a black and white image based on the image data input by the input unit. Means, by performing a predetermined image processing on the image data input by the input means, data generating means for generating image data of each color for color image formation and black image data for black and white image formation, Among the image data generated by the data generating means, a first storage unit that stores the image data of each color for forming the color image, and a second storage that stores the black image data for forming the black and white image A color image stored in the first storage unit when the determination unit determines that the image to be formed is a color image. When the image data of each color for formation is selected, and the determination unit determines that the image to be formed is a black-and-white image, the black image for black-and-white image formation stored in the second storage unit A color image forming apparatus comprising: a selection unit that selects data; and an image forming unit that forms an image based on the image data selected by the selection unit. 2. An input unit for inputting image data based on an image to be formed, and determining whether the image to be formed is a color image or a monochrome image based on the image data input by the input unit. Means for performing predetermined image processing on the image data input by the input means to generate image data of each color for forming a color image; and the color image generated by the data generating means A storage unit for storing image data of each color for formation; and an image of each color for color image formation stored in the storage unit when the determination unit determines that the image to be formed is a color image. When data is selected and the determination unit determines that the formed image is a black and white image, the color stored in the storage unit is determined. Selecting means for synthesizing image data of each color for image formation and selecting the synthesized output as black image data; and image forming means for forming an image based on the image data selected by the selecting means. Characteristic color image forming apparatus.